Multi-analytical investigation on felt-tip pen inks: Formulation and preliminary photo-degradation study

We present a multi-analytical study on the formulation of commercial felt-tip pens, introduced in the second half of the 20th century and commonly used by modern and contemporary artists. These media of both drawing and writing have not yet been fully investigated, but the degradation processes they might undergo, such as fading, are well-known and rather apparent. Twelve water-based felt-tip pens were investigated by the joint use of complementary analytical techniques, such as Thin Layer Chromatography, Nuclear Magnetic Resonance, Fourier transformed infrared spectroscopy, X-ray fluorescence spectrometry and Pyrolysis-Gas Chromatography/Mass Spectrometry. The obtained results provided crucial, preliminary data for the identification of dyes, solvents and additives present in the inks' formulations. Numerous synthetic food coloring agents and pigments were identified, such as Acid Yellow 23, Acid Red 18, Acid Blue 9, and Pigment Blue 15. In addition, glycols, fatty acids, 2-phenoxyethanol, colophony, benzotriazole derivatives and other solvents and additives were detected in the manufactured inks. Furthermore, the effects of photo-degradation on one emblematic ink sample were studied, highlighting in particular visual and aesthetical changes due to discoloration. This study demonstrates a methodology based upon the use of an integrated analytical approach for the characterization of commercial ink-based artistic media and their viable degradation patterns, which aims to develop suitable conservation treatments to assess modern and contemporary drawings and writings.